At Centennial Contracting & Roofing, we often meet homeowners who are researching attic insulation long before they ever need a roof repair. During that process, one term comes up again and again: R-value. Understanding R-value is one of the most important steps you can take to improve your home’s comfort, lower energy costs, and protect the lifespan of your roof. What Is R-Value? R-value measures how well insulation resists heat flow. Simply put, the higher the R-value, the